Apply texture/ structure to a plane with an image
The simplest way to put an image as the texture of a plane is using the import images as planes add on. Go to edit, preferences, add-ons and search images as planes. Click the checkbox next to the add on and close the preferences window. Now, press ShiftA to add to scene. Then, in the mesh menu there should be an option image as plane. Select that option, and choose your image. Please upvote and mark as accepted answer if this helps.
EDIT 
Based on what you are asking, instead of putting the texture into the displacement slot, you should add a mix node, connect that to the surface slot, put the current Principled BSDF node into the top slot and add a second Principled BSDF node with the image texture there. Fiddle with the alpha slider until it looks how you want. 
I'm on my phone right now, so I cannot guarantee that this answer will work. I will edit this response if this doesn't help, and I'll get onto my computer to test the answer first. However, if this helps, then you're welcome :).